As it is known the self-contained electrical ovens allow the food to be heat treated and baked. At the present status of art some ovens are equipped with multiple electrical resistances placed in the section of the oven underlying the baking room. Some other ovens are also provided with resistances placed in the section of the oven overlying the baking room. Both resistances assemblies are connected to thermostatic means embodied in the electrical resistances.
Such a construction causes a lot of troubles especially due to the indirect thermic control of the baking room which is carried out on the body of the above mentioned resistances.
The heat generated by and stored in the resistance assemblies of the upper section, as well as transmitted by infrared radiations to the baking room, causes frequent power supply cutoff effected by the thermostatic device even before an effective treatment of the food. The differential operating times of the bimetallic thermostats due to the hysteresis of the plates and the non-dispersed heat latent therein, in the above mentioned arrangement of the resistance assemblies, are generally very frequent and above all not suitable to the thermic conditions and the actual transmitted heat in particular to the center of the baking room.
Such an operation under these conditions causes among other harmful effects outward cold flows of the mass humidity with the consequences of a less effective thermic treatment.
In order either to prevent or to restrict the reiterated power supply cutoff in the common application it is customary to open the door of the oven so as to reduce the frequency of the thermostat operations.
In case of resistances equipped with thermostats embodied in or directly connected to the resistance shanks it is self evident that the drawback caused by carrying out the control of the heat generated by the resistance instead of controlling the heat in the baking room generates a lack of thermic balance.
In case of controlling both functions the above mentioned troubles make it necessary the application of limiting devices for one of the functions.
It is also self evident that the used thermostats, the mechanical and electrical connections of the several regulation and control members and safety devices necessary to achieve satisfying results are causing relevant manufacturing costs due also to the modular and multiple resistances used to achieve different heat developments.
The direct control of the actual heat in the baking room has not been carried out in any of the above mentioned embodiment.